Muffler and heat shield assembly

ABSTRACT

A muffler assembly includes an outer shell defining an internal cavity that extends between first and second ends. A first end cap is attached to the first end and a second end cap is attached to the second end. The first and second end caps provide a substantially enclosed internal cavity within the outer shell. A heat shield extends along a length of the outer shell and has a first shield end attached to the first end cap and a second shield end attached to the second end cap. The first and second shield ends are deformed around an outer perimeter of the first and second ends caps, or separate retaining members are used to secure the first and second shield ends to the first and second end caps.

TECHNICAL FIELD

The subject invention relates to a method and apparatus for attaching a heat shield to a muffler.

BACKGROUND OF THE INVENTION

A vehicle exhaust system includes a plurality of exhaust components that handle exhaust gases generated by an internal combustion engine. A typical exhaust system includes an exhaust pipe that guides exhaust gases from the internal combustion engine to a muffler. A tailpipe transfers exhaust gases from the muffler to external atmosphere. In addition to guiding exhaust gases, the muffler reduces operational noise levels generated by the internal combustion engine and exhaust system. The exhaust system can include other exhaust components for processing exhaust gases or for reducing noise, such as additional silencers, a catalytic converter, or a resonator.

The exhaust components are typically routed from the internal combustion engine, located near a front portion of a vehicle, underneath a passenger compartment to a rear portion of the vehicle where the tailpipe is traditionally located. The muffler is typically positioned directly underneath the passenger compartment. As known, the exhaust gases generated by the exhaust system have high temperatures. Due to the proximity of the muffler to the passenger component, there is a concern that this heat could be transferred to the passenger compartment.

One solution to reduce effects of the heat generated by exhaust system components has been to install a heat shield between the muffler and a vehicle structure such as a vehicle floor. Many different methods have been used to attach the heat shield to the muffler. One known method involves using bands to secure the heat shield to the muffler. A banding machine typically secures a band around the heat shield at each end of the muffler. This method has some disadvantages. One disadvantage is that the bands may not be secured tightly enough to the muffler. Loose bands can generate an annoying rattle sound. Another disadvantage involves the size, maintenance, and overall cost of the banding machine.

Another known attachment method uses a weld to attach the heat shield to the muffler. Typically in this method, the heat shield is welded directly to an outer shell of the muffler. This weld interface does not accommodate thermal expansion that occurs as the muffler heats up and cools down. This can adversely affect the welds and can even result in weld failures.

Another known attachment method involves capturing ends of the heat shield under a spun end of a muffler end cap. A muffler includes an outer shell with a muffler end cap mounted to each end of the outer shell. In a spin process, ends of the outer shell and circumferential edges of the muffler end caps are spun or folded over each other to provide a secure and permanent attachment between the muffler end caps and the outer shell. Attempting to capture another layer of material, i.e. a heat shield end portion, in the muffler end cap spun end can be disruptive to the assembly process. Further, muffler leak rate properties can be degraded due to the additional layer of material at the spun joint.

Thus, there is a need for an improved attachment interface between a heat shield and a muffler assembly that can accommodate thermal expansion without degrading the attachment interfaces, and which is more reliable than prior attachment interfaces.

SUMMARY OF THE INVENTION

A muffler assembly includes an outer shell having a first end cap at one shell end and a second end cap at an opposite shell end. The first and second end caps are attached to the outer shell via a spin attachment process. A heat shield extends along a length of the outer shell and includes a first shield end attached over the first end cap at a first attachment interface and a second shield end attached over the second end cap at a second attachment interface.

In one example, the first and second attachment interfaces are provided by deforming the first and second shield ends around at least a portion of a perimeter of the first and second end caps. In another example, at least one retaining member is used to provide the first and second attachment interfaces. The retaining member could be a single clip, multiple clips, or a retaining ring that directly secures the first and second heat shield ends to the first and second end caps.

In one embodiment, the heat shield includes a plurality of convolutes that are spaced apart from each other along a length of the heat shield. Each convolute is formed as an accordion-like protrusion extending outwardly from an upper surface of the heat shield. The plurality of convolutes dissipates stress that would be generated at the first and second attachment interfaces as the muffler assembly heats up and cools down.

In another embodiment, the heat shield is made from a first component and a second component attached to the first component via an adjustable attachment interface. The adjustable attachment interface allows an overall length of the heat shield to be adjusted to any one of a plurality of overall lengths within a predetermined range of overall lengths. The adjustable attachment interface includes at least one longitudinal slot formed in at least one of the first or second components and at least one fastener received within the longitudinal slot to secure the first and second components together.

The subject invention provides an improved method and apparatus for attaching a heat shield to a muffler assembly. The improved method and apparatus can accommodate thermal expansion without degrading attachment interfaces, is more reliable than prior attachment interfaces, and has improved acoustics over prior designs. These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a muffler and heat shield assembly incorporating the subject invention.

FIG. 2A is a partial cross-sectional view of one example of an attachment interface between a heat shield and a muffler.

FIG. 2B is an end view of another example of an attachment interface between a heat shield and a muffler.

FIG. 3 is a partial cross-sectional view of another example of an attachment interface between a heat shield and a muffler.

FIG. 4A is a partial cross-sectional view of another example of an attachment interface between a heat shield and a muffler.

FIG. 4B is an enlarged partial cross-section showing a portion of the attachment interface of FIG. 4A.

FIG. 4C is an end view of the attachment interface of FIG. 4A.

FIG. 5 is a side view of an example of a heat shield including convolutes.

FIG. 6 is a side view of an example of an adjustable length heat shield assembly.

FIG. 7 is an enlarged detail view of circled portion 7 shown in FIG. 6.

FIG. 8 is a top view of the detail of FIG. 7.

FIG. 9 is a side view of a washer used in the attachment shown in FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A muffler 10, shown in FIG. 1, includes an outer shell 12, a first end cap 14 mounted to one end of the outer shell 12, and a second end cap 16 mounted to an opposite end of the outer shell 12. The first 14 and second 16 end caps are attached to the outer shell 12 by using a spin process. This spin process is well-known in the art and will not be discussed in detail.

A heat shield 18 is mounted to the muffler 10 to reduce adverse effects of heat generated by the muffler 10. The heat shield 18 has a first shield end 20 mounted to the first end cap 14 at a first attachment interface and a second shield end 22 mounted to the second end cap 16 at a second attachment interface. The heat shield 18 extends along an upper length of the outer shell 12 and is to be positioned between the muffler 10 and a vehicle structure, such as a floor (not shown).

The heat shield 18 can be attached to the first 14 and second 16 end caps in many different manners to define the first and second attachment interfaces. In one example, at least one retaining clip 24 is used to secure each of the first 20 and second 22 shield ends to the respective first 14 and second 16 end caps. A detail of the retaining clip 24 is shown in FIG. 2A for attaching the first shield end 20 to the first end cap 14. It should be understood that the second shield end 22 would be attached to the second end cap 16 in a similar manner.

As shown in FIG. 2A, the outer shell 12 includes an outer end 28 and the first end cap 14 includes an outer peripheral edge 30. The spin process aligns the outer end 28 and outer peripheral edge 30 and spins or folds the outer peripheral edge 30 over the outer end 28 to form a muffler end cap spin attachment, shown generally at 32. The first shield end 20 is positioned over the muffler end cap spin attachment 32 and the retaining clip 24 is used to secure the heat shield 18 to the first end cap 14.

In this attachment configuration, the first shield end 20 directly engages an end cap portion adjacent the outer peripheral edge 30. The retaining clip 24 has a first portion 36 that directly engages the first shield end 20 and a second portion 38 that directly engages an external surface 40 of the first end cap 14.

A single retaining clip can be used to secure the heat shield 18 to the muffler 10 or a plurality of retaining clips 24, as shown in FIG. 2B, can be used to secure the heat shield 18 to the muffler 10. The first shield end 20 is attached to the first end cap 14 preferably only along an upper portion of the first end cap 14. The single retaining clip 24 can be positioned anywhere along the upper portion. Optionally, the single retaining clip 24 could be configured to extend continuously along the upper portion.

In the attachment configuration shown in FIG. 2B, each retaining clip 24 is spaced apart from an adjacent retaining clip 24 along the upper portion. The number of retaining clips 24 needed may vary depending upon muffler size, vehicle application, or other known characteristics.

As shown in FIG. 2A, the heat shield includes a body portion 42 that is spaced apart from an external surface 44 of the outer shell 12 to define a gap 46. The gap 46 allows the body portion 42 to flex or move to accommodate thermal expansion as the muffler 10 heats up and cools down. The heat shield 18 is shown in a thermally expanded position in FIG. 2A. An example of a heat shield position at a cooler temperature is shown by dashed lines at 48. During thermal expansion, a small amount of relative movement occurs between the first shield end 20 and the first end cap 14. The retaining clip 24 allows sufficient movement to accommodate thermal expansion but prohibits separation of the heat shield 18 from the muffler. The invention also prohibits any rattling noise.

The retaining clip 24 can be formed from a resilient spring material that is snapped over the first end cap 14. The retaining clip 24 could also be deformed over the muffler end cap spin attachment 32 with tack welds being used if needed. An example of a tack weld location is shown at 50. The retaining clip 24 could also be staked in place using a manual or automated process. Optionally, the first end cap 14 could include a retention feature 52 that cooperates with the retaining clip 24 to provide a more secure attachment interface as needed.

Another attachment interface 54 for attaching the first shield end 20 to the first end cap 14 is shown in FIG. 3. It should be understood that the second shield end 22 would be attached to the second end cap 16 in a similar manner. This attachment interface 54 includes deforming the first shield end 20 around the muffler end cap spin attachment 32. The first shield end 20 is thus mechanically locked in place by forming or crimping the first shield end 20 over the muffler end cap spin attachment 32. Staking operations could also be performed after attachment to provide a more secure attachment as needed. One benefit with this configuration is that additional hardware, such as clips, is eliminated.

Another attachment interface 60 for attaching the first shield end 20 to the first end cap 14 is shown in FIGS. 4A-4C. It should be understood that the second shield end 22 would be attached to the second end cap 16 in a similar manner. This attachment interface 60 includes the use of a retaining ring 62 that is snapped over, formed over, or crimped over the first shield end 20 and the muffler end cap spin attachment 32.

As shown in FIG. 4A, the heat shield 18 only covers an upper portion of the outer shell 12. In this attachment configuration, the retaining ring 62 is installed over the entire perimeter of the first end cap 14. As shown in FIG. 4B, the retaining ring 62 includes a first portion 64 that directly engages the first shield end 20 and a second portion 66 that directly engages the external surface 40 of the first end cap 14. Crimping or staking, as indicated at 68 in FIG. 4C, could also be used as needed. The retaining ring 62 can be formed from resilient spring steel or other similar material.

As discussed above, the heat shield 18 can be attached to the first 14 and second 16 end caps in many different manners to define the first and second attachment interfaces. FIGS. 2A-2B, 3, and 4A-4C show different examples of these attachment interfaces. It should be understood that similar attachments could be used for both the first and second attachment interfaces, or different attachments could be used for each of the first and second attachment interfaces. Further, each attachment interface could be used with different types of heat shields.

One example of a heat shield is shown generally at 70 in FIG. 5. In this configuration, the heat shield includes a longitudinally extending body 72 that is attached to the first 14 and second 16 end caps by any of the attachment methods described above. The longitudinally extending body includes a plurality of convolutes 76 that extend outwardly, away from the outer shell 12. The convolutes 76 are positioned transverse to a longitudinal axis L defined by the longitudinally extending body 72. The convolutes 76 allow the heat shield 70 to flex in a manner similar to movement of an accordion. This flexing movement occurs as the muffler 10 heats up and cools down. This movement dissipates stress that would otherwise attempt to degrade heat shield/end cap attachment interfaces.

Another example of a heat shield 80 is shown in FIG. 6. In this example, the heat shield 80 includes a first portion 82 and a second portion 84 that is attached to the first portion 82 via an adjustable attachment interface 100. The adjustable attachment interface 100 allows the overall length of the heat shield 80 to be adjusted between a plurality of overall lengths within a predetermined range of overall lengths.

In the example shown, the first 82 and second 84 portions overlap and are connected with a series of Belleville washers 86 and fasteners, such as rivets 88. At least one of the first 82 and second 84 portions includes a series of slots 90 that receive the rivets 88. Strengthening ribs 92 are formed on the first 82 and second 84 portions. The strengthening ribs 92 extend generally parallel to a longitudinal axis L defined by the heat shield 80.

An example of a rivet 88 being received within a slot 90 is shown in FIG. 7. The Belleville washer 86 is positioned on an external surface 94 of the first 82 or second 84 portion depending on which of the first 82 or second 84 portions is overlaid on top of the other of the first 82 or second 84 portions. The rivet 88 and Belleville washer 86 can be moved linearly back and forth within the slot 90 (see FIG. 8) to adjust the overall length. The Belleville washer 86 includes turned up edges 96 (see FIG. 9) to prevent the Belleville washer 86 from digging into the heat shield 80.

The linear movement allows adjustment of the heat shield 80 prior to attaching the heat shield 80 to the first 14 and second end caps 16 as described above. This allows a common heat shield assembly to be used for mufflers 10 of different lengths within a predetermined range. Also, mufflers of even greater or lesser lengths than the predetermined range could also benefit from this type of heat shield 80 as only one of the first 82 or second 84 portions would have to be changed to accommodate the variable length.

Further, the linear movement of the rivet 88 within the slot 90 can occur during vehicle operation. This allows for the difference in thermal expansion between the muffler 10 and the heat shield 80 generated during normal thermal cycling. This helps to dissipate stress that would otherwise attempt to degrade heat shield/end cap attachment interfaces. The Belleville washers 86 keep tension on the adjustable attachment interface 100, which allows this relative movement without having looseness or rattling.

Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention. 

1. A muffler assembly comprising: an outer shell extending between first and second ends; a first end cap attached to said first end; a second end cap attached to said second end; and a heat shield extending along a length of said outer shell wherein a first shield end is mounted over said first end cap at a first attachment interface and a second shield end is mounted over said second end cap at a second attachment interface.
 2. The muffler assembly according to claim 1 wherein said first and second end caps are attached to said first and second ends at a spun attachment interface with said first shield end engaging an external surface of said first end cap and said second shield end engaging an external surface of said second end cap.
 3. The muffler assembly according to claim 2 wherein said first shield end includes a first deformed portion to define said first attachment interface and said second shield end includes a second deformed portion to define said second attachment interface and wherein said first and second deformed portions are deformed over said spun attachment interface.
 4. The muffler assembly according to claim 2 including a first retaining ring cooperating with said first shield end to define said first attachment interface and a second retaining ring cooperating with said second shield end to define said second attachment interface.
 5. The muffler assembly according to claim 4 wherein said first retaining ring extends continuously about an outer perimeter of said first end cap and said second retaining ring extends continuously about an outer perimeter of said second end cap, said first retaining ring directly engaging said first shield end and said spun attachment interface and said second retaining ring directly engaging said second shield end and said spun attachment interface.
 6. The muffler assembly according to claim 5 wherein said heat shield surrounds only an upper portion of said outer shell with a lower surface of a center portion, said heat shield being spaced apart from an external surface of said outer shell to define a gap.
 7. The muffler assembly according to claim 2 including at least one first retaining clip securing said first shield end to said first end cap to define said first attachment interface and at least one second retaining clip securing said second shield end to said second end cap to define said second attachment interface.
 8. The muffler assembly according to claim 7 wherein said first and second retaining clips are formed from a resilient spring steel material.
 9. The muffler assembly according to claim 7 wherein said at least one first retaining clip comprises a first plurality of retaining clips with each of said first plurality of retaining clips securing said first shield end to said spun attachment interface at said first end cap and wherein said at least one second retaining clip comprises a second plurality of retaining clips with each of said second plurality of retaining clips securing said second shield end to said spun attachment interface at said second end cap.
 10. The muffler assembly according to claim 9 wherein said heat shield surrounds only an upper portion of said outer shell with a lower surface of a center portion, said heat shield being spaced apart from an external surface of said outer shell to define a gap and wherein said first and second pluralities of retaining clips are spaced apart from each other about an outer perimeter of said heat shield.
 11. The muffler assembly according to claim 7 wherein said first end cap includes at least one first retention feature that cooperates with said at least one first retaining clip to fix said at least one first retaining clip to said first end cap and wherein said second end cap includes at least one second retention feature that cooperates with said at least one second retaining clip to fix said at least one second retaining clip to said second end cap.
 12. The muffler assembly according to claim 2 wherein said heat shield includes a plurality of convolutes spaced apart from each other along a length of said heat shield.
 13. The muffler assembly according to claim 12 wherein said heat shield defines a longitudinal axis extending along the length of said heat shield and wherein each convolute comprises a raised accordion projection formed on an upper surface of said heat shield with each of said raised accordion projections extending in a direction transverse to said longitudinal axis.
 14. The muffler assembly according to claim 2 wherein said heat shield includes a first shield component and a second shield component secured to said first shield component with an adjustable shield attachment interface.
 15. The muffler assembly according to claim 14 wherein said adjustable shield attachment interface includes at least one longitudinal slot being formed in one of said first and second shield components and at least one fastener extending through said at least one longitudinal slot to secure said first and second shield components to each other.
 16. The muffler assembly according to claim 15 wherein said at least one fastener is linearly movable within said at least one longitudinal slot to adjust an overall length of said heat shield within a predetermined overall length range.
 17. The muffler assembly according to claim 14 wherein said first and second shield components each include a plurality of stiffening ribs extending outwardly from an upper surface of said first and second shield components.
 18. The muffler assembly according to claim 1 wherein said first attachment interface is different than said second attachment interface.
 19. A method for assembling at heat shield to a muffler comprising: providing an outer shell having a first end cap attached to a first shell end and a second end cap attached to a second shell end; securing a first heat shield end directly over the first end cap at a first attachment interface; and securing a second heat shield end directly over the second end cap at a second attachment interface.
 20. The method according to claim 19 including deforming the first heat shield end about an outer perimeter of said first end cap to form the first attachment interface and deforming the second heat shield end about an outer perimeter of said second end cap to form the second attachment interface.
 21. The method according to claim 19 including attaching the first heat shield end to the first end cap with at least one first retaining member to form the first attachment interface and attaching the second heat shield end to the second end cap with at least one second retaining member to form the second attachment interface. 